Wireless communications networks are known. In a cellular system, radio coverage is provided to user equipment, for example mobile telephones, by geographical area. Those geographical areas of radio coverage are known as cells. A base station is located in each geographical area to provide the required radio coverage. A base station may support more than one cell providing coverage in the same geographical area. User equipment in the area served by a base station receives information and data from the base station and transmits information and data to the base station.
Information and data transmitted by the base station to the user equipment occurs on channels of radio carries known as downlink carriers. Information and data transmitted by user equipment to the base station occurs on uplink channels of radio carriers known as uplink carriers.
In known wireless telecommunications networks, user equipment can move between geographical base station coverage areas. Services provided to user equipment is typically overseen by a radio network controller (RNC). The radio network controller communicates with user equipment and base stations and determines which base station each user equipment is primarily connected to. Furthermore, the radio network controller acts to control and communicate with a base station and user equipment when the user equipment moves from the geographical area served by one base station to a geographical area served by another base station or between geographical areas served by the same base station.
The area served by a given base station typically comprises several sectors which together define a coverage area for that base station. Typically, a base station serves three sectors. Those sectors are typically served by separate antenna arrays provided on the base station. As well as controlling movement between base station coverage areas, the radio network controller also has visibility of, and communicates with, a base station and user equipment when the user equipment moves between sectors within a coverage area served by a single base station.
Movement between the sectors provided by a single base station and movement between base stations are known as a “mobility event” or a “relocation” and are overseen by the radio network controller. Typically, the extent of the involvement of the radio network controller in such mobility events or relocations will also depend upon the current state of the user equipment. For example, relocation of user equipment when in an active state (i.e. actively supporting the communication of data between the user equipment and a source base station) involves controlling the handover from the source base station to a target base station identified by a measurement report provided by the user equipment which identifies the measured characteristics of signals received from that target base station. However, relocation during an inactive state (such as an idle mode) may not require the involvement of the radio network controller to enable the user equipment to relocate to the target base station.
As the configuration and arrangement of network nodes such as base stations within the wireless communications network becomes increasingly complex, unexpected situations can occur which reduce the likelihood of a successful relocation occurring.
Accordingly, it is desired to provide an improved technique for facilitating relocation.